/*
 * Copyright (c) 1998 Michael Smith.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>

#include "stand.h"

#include <sys/stat.h>
#include <string.h>
#include <zlib.h>

#define	Z_BUFSIZE 2048	/* XXX larger? */

struct z_file
{
	int		zf_rawfd;
	off_t		zf_dataoffset;
	z_stream	zf_zstream;
	unsigned char	zf_buf[Z_BUFSIZE];
	int		zf_endseen;
};

static int zf_fill(struct z_file *z);
static int zf_open(const char *path, struct open_file *f);
static int zf_close(struct open_file *f);
static int zf_read(struct open_file *f, void *buf, size_t size, size_t *resid);
static off_t zf_seek(struct open_file *f, off_t offset, int where);
static int zf_stat(struct open_file *f, struct stat *sb);

struct fs_ops gzipfs_fsops = {
	.fs_name = "zip",
	.fo_open = zf_open,
	.fo_close = zf_close,
	.fo_read = zf_read,
	.fo_write = null_write,
	.fo_seek = zf_seek,
	.fo_stat = zf_stat,
	.fo_readdir = null_readdir
};

static int
zf_fill(struct z_file *zf)
{
	int	result;
	int	req;

	req = Z_BUFSIZE - zf->zf_zstream.avail_in;
	result = 0;

	/* If we need more */
	if (req > 0) {
		/* move old data to bottom of buffer */
		if (req < Z_BUFSIZE)
			bcopy(zf->zf_buf + req, zf->zf_buf, Z_BUFSIZE - req);

		/* read to fill buffer and update availibility data */
		result = read(zf->zf_rawfd,
		    zf->zf_buf + zf->zf_zstream.avail_in, req);
		zf->zf_zstream.next_in = zf->zf_buf;
		if (result >= 0)
			zf->zf_zstream.avail_in += result;
	}
	return (result);
}

/*
 * Adapted from get_byte/check_header in libz
 *
 * Returns 0 if the header is OK, nonzero if not.
 */
static int
get_byte(struct z_file *zf, off_t *curoffp)
{
	if ((zf->zf_zstream.avail_in == 0) && (zf_fill(zf) == -1))
		return (-1);
	zf->zf_zstream.avail_in--;
	++*curoffp;
	return (*(zf->zf_zstream.next_in)++);
}

static int gz_magic[2] = {0x1f, 0x8b}; /* gzip magic header */

/* gzip flag byte */
#define	ASCII_FLAG	0x01 /* bit 0 set: file probably ascii text */
#define	HEAD_CRC	0x02 /* bit 1 set: header CRC present */
#define	EXTRA_FIELD	0x04 /* bit 2 set: extra field present */
#define	ORIG_NAME	0x08 /* bit 3 set: original file name present */
#define	COMMENT		0x10 /* bit 4 set: file comment present */
#define	RESERVED	0xE0 /* bits 5..7: reserved */

static int
check_header(struct z_file *zf)
{
	int	method; /* method byte */
	int	flags;  /* flags byte */
	uInt	len;
	int	c;

	zf->zf_dataoffset = 0;
	/* Check the gzip magic header */
	for (len = 0; len < 2; len++) {
		c = get_byte(zf, &zf->zf_dataoffset);
		if (c != gz_magic[len]) {
			return (1);
		}
	}
	method = get_byte(zf, &zf->zf_dataoffset);
	flags = get_byte(zf, &zf->zf_dataoffset);
	if (method != Z_DEFLATED || (flags & RESERVED) != 0) {
		return (1);
	}

	/* Discard time, xflags and OS code: */
	for (len = 0; len < 6; len++)
		(void) get_byte(zf, &zf->zf_dataoffset);

	if ((flags & EXTRA_FIELD) != 0) { /* skip the extra field */
		len  =  (uInt)get_byte(zf, &zf->zf_dataoffset);
		len += ((uInt)get_byte(zf, &zf->zf_dataoffset))<<8;
		/* len is garbage if EOF but the loop below will quit anyway */
		while (len-- != 0 && get_byte(zf, &zf->zf_dataoffset) != -1)
			;
	}
	if ((flags & ORIG_NAME) != 0) { /* skip the original file name */
		while ((c = get_byte(zf, &zf->zf_dataoffset)) != 0 && c != -1)
			;
	}
	if ((flags & COMMENT) != 0) {   /* skip the .gz file comment */
		while ((c = get_byte(zf, &zf->zf_dataoffset)) != 0 && c != -1)
			;
	}
	if ((flags & HEAD_CRC) != 0) {  /* skip the header crc */
		for (len = 0; len < 2; len++)
			c = get_byte(zf, &zf->zf_dataoffset);
	}
	/* if there's data left, we're in business */
	return ((c == -1) ? 1 : 0);
}

static int
zf_open(const char *fname, struct open_file *f)
{
	char		*zfname;
	int		rawfd;
	struct z_file	*zf;
	char		*cp;
	int		error;
	struct stat	sb;

	/* Have to be in "just read it" mode */
	if (f->f_flags != F_READ)
		return (EPERM);

	/* If the name already ends in .gz or .bz2, ignore it */
	if ((cp = strrchr(fname, '.')) && (strcmp(cp, ".gz") == 0 ||
	    strcmp(cp, ".bz2") == 0 || strcmp(cp, ".split") == 0))
		return (ENOENT);

	/* Try to open the compressed datafile */
	rawfd = open(fname, O_RDONLY | F_GZIP);
	if (rawfd == -1) {
		/* add .gz sufix and try again */
		zfname = malloc(strlen(fname) + 4);
		if (zfname == NULL)
			return (ENOMEM);
		sprintf(zfname, "%s.gz", fname);
		rawfd = open(zfname, O_RDONLY);
		free(zfname);
		if (rawfd == -1)
			return (ENOENT);
	}

	if (fstat(rawfd, &sb) < 0) {
		printf("zf_open: stat failed\n");
		close(rawfd);
		return (ENOENT);
	}
	if (!S_ISREG(sb.st_mode)) {
		close(rawfd);
		return (EISDIR);	/* best guess */
	}

	/* Allocate a z_file structure, populate it */
	zf = malloc(sizeof (struct z_file));
	if (zf == NULL)
		return (ENOMEM);
	bzero(zf, sizeof (struct z_file));
	zf->zf_rawfd = rawfd;

	/* Verify that the file is gzipped */
	if (check_header(zf)) {
		close(zf->zf_rawfd);
		free(zf);
		return (EFTYPE);
	}

	/* Initialise the inflation engine */
	if ((error = inflateInit2(&(zf->zf_zstream), -15)) != Z_OK) {
		printf("zf_open: inflateInit returned %d : %s\n", error,
		    zf->zf_zstream.msg);
		close(zf->zf_rawfd);
		free(zf);
		return (EIO);
	}

	/* Looks OK, we'll take it */
	f->f_fsdata = zf;
	return (0);
}

static int
zf_close(struct open_file *f)
{
	struct z_file	*zf = (struct z_file *)f->f_fsdata;

	inflateEnd(&(zf->zf_zstream));
	close(zf->zf_rawfd);
	free(zf);
	return (0);
}

static int
zf_read(struct open_file *f, void *buf, size_t size, size_t *resid)
{
	struct z_file	*zf = (struct z_file *)f->f_fsdata;
	int		error;

	zf->zf_zstream.next_out = buf;		/* where and how much */
	zf->zf_zstream.avail_out = size;

	while (zf->zf_zstream.avail_out && zf->zf_endseen == 0) {
		if ((zf->zf_zstream.avail_in == 0) && (zf_fill(zf) == -1)) {
			printf("zf_read: fill error\n");
			return (EIO);
		}
		if (zf->zf_zstream.avail_in == 0) { /* oops, unexpected EOF */
			printf("zf_read: unexpected EOF\n");
			if (zf->zf_zstream.avail_out == size)
				return (EIO);
			break;
		}

		/* decompression pass */
		error = inflate(&zf->zf_zstream, Z_SYNC_FLUSH);
		if (error == Z_STREAM_END) {	/* EOF, all done */
			zf->zf_endseen = 1;
			break;
		}
		if (error != Z_OK) {		/* argh, decompression error */
			printf("inflate: %s\n", zf->zf_zstream.msg);
			return (EIO);
		}
	}
	if (resid != NULL)
		*resid = zf->zf_zstream.avail_out;
	return (0);
}

static int
zf_rewind(struct open_file *f)
{
	struct z_file	*zf = (struct z_file *)f->f_fsdata;

	if (lseek(zf->zf_rawfd, zf->zf_dataoffset, SEEK_SET) == -1)
		return (-1);
	zf->zf_zstream.avail_in = 0;
	zf->zf_zstream.next_in = NULL;
	zf->zf_endseen = 0;
	(void) inflateReset(&zf->zf_zstream);

	return (0);
}

static off_t
zf_seek(struct open_file *f, off_t offset, int where)
{
	struct z_file	*zf = (struct z_file *)f->f_fsdata;
	off_t		target;
	char		discard[16];

	switch (where) {
	case SEEK_SET:
		target = offset;
		break;
	case SEEK_CUR:
		target = offset + zf->zf_zstream.total_out;
		break;
	default:
		errno = EINVAL;
		return (-1);
	}

	/* rewind if required */
	if (target < zf->zf_zstream.total_out && zf_rewind(f) != 0)
		return (-1);

	/* skip forwards if required */
	while (target > zf->zf_zstream.total_out) {
		errno = zf_read(f, discard, min(sizeof (discard),
		    target - zf->zf_zstream.total_out), NULL);
		if (errno != 0)
			return (-1);
	}
	/* This is where we are (be honest if we overshot) */
	return (zf->zf_zstream.total_out);
}


static int
zf_stat(struct open_file *f, struct stat *sb)
{
	struct z_file	*zf = (struct z_file *)f->f_fsdata;
	int		result;
	off_t		pos1, pos2;
	uint32_t	size;

	/* stat as normal, but indicate that size is unknown */
	if ((result = fstat(zf->zf_rawfd, sb)) == 0) {
		if (sb->st_size == -1)
			return (result);
		pos1 = lseek(zf->zf_rawfd, 0, SEEK_CUR);
		pos2 = lseek(zf->zf_rawfd, sb->st_size - 4, SEEK_SET);
		if (pos2 != -1) {
			if (read(zf->zf_rawfd, &size, 4) == 4)
				sb->st_size = (off_t)size;
			else
				sb->st_size = -1;
		} else
			sb->st_size = -1;

		pos1 = lseek(zf->zf_rawfd, pos1, SEEK_SET);
	}
	return (result);
}
